Previously, settling tanks having suction filters for the separation of solid particles from liquid comprised turbine pumps hanging freely or suspended in vertical standpipes of liquid, the bottoms of which standpipes were connected to the suction chamber of the filter and the pumps were sealed to the top of their standpipes. However, if the seal leaked or if one of the pumps were to be removed, air would enter the suction chamber and intakes of the other pumps, causing cavitation unless the system were shut down. In order to avoid this, the lower depending inlet end of the pump was then sealed into an aperture in the suction chamber, but this was an expensive arrangement and the O-ring seal often became damaged, causing leakage. Also the system had to be shut down if a pump had to be removed for repair and maintenance, and during which time the aperture to the suction chamber needed to be plugged. Such a plug was particularly necessary if the suspended pump extended through the dirty liquid into the suction chamber containing clean liquid.
Thus, to avoid the requirement of a liquid-tight seal in the aperture to the suction chamber, the suction chamber was then placed beneath the clean tank so that in the event there were any leakage, such would not produce contamination, and the fitting between the intake end of the pump and the aperture in the clean tank could be an hydraulic slip-fit with a very narrow annular clearance between the aperture and the intake of the pump. Still, if the pump were to be removed, the system would have to be shut down and the aperture plugged, if the other pumps were to be operated.